A nurse is collecting data from a client who is receiving clopidogrel following the placement of a cardiac stent. Which of the following findings should the nurse identify as an adverse effect of this medication?

A. Ferrous sulfate: This is an iron supplement and wouldn't be used to reverse warfarin's anticoagulant effect.

B. Prednisone: This is a steroid medication used for various inflammatory conditions and wouldn't be used to address excessive blood thinning.

C. Vitamin K: Vitamin K is the antidote for warfarin poisoning or excessive anticoagulation. By providing vitamin K, the body can resume producing clotting factors, counteracting warfarin's effect.

D. Heparin: This is another blood thinner medication. While it can be used in specific situations, it wouldn't be the first choice to reverse warfarin's effect because it adds another layer of anticoagulation, which could be risky.

A. Increase the risk for bleeding: Herbal supplements like green tea, ginkgo, feverfew, garlic, and ginger can potentiate the effects of warfarin by enhancing its anticoagulant properties. This increases the risk of bleeding, as warfarin itself is a blood thinner designed to prevent clot formation. These herbs can further inhibit platelet aggregation or enhance anticoagulation, leading to a higher risk of bleeding complications.

B. Cause severe headache: While some herbal supplements can cause headaches as a side effect, this is not the primary concern when combined with warfarin. The interaction between these herbs and warfarin does not commonly result in severe headaches. The primary issue is the increased risk of bleeding.

C. Decrease the effects of the warfarin (Coumadin): These particular herbal supplements do not generally decrease the effects of warfarin. In fact, they are more likely to increase its anticoagulant effects. Some other substances might interfere with warfarin's efficacy, but the herbs listed are known to enhance its bleeding risk.

D. Cause severe hypotension: Severe hypotension is not a common result of combining these herbal supplements with warfarin. The primary interaction is related to the blood-thinning effects, not to blood pressure regulation. Herbal supplements that might affect blood pressure are not typically those that interact significantly with warfarin in this manner.